Telecommunications – Radiotelephone system – Zoned or cellular telephone system
Reexamination Certificate
1998-05-28
2001-02-13
Bost, Dwayne (Department: 2681)
Telecommunications
Radiotelephone system
Zoned or cellular telephone system
C455S436000, C455S437000, C455S438000, C455S440000
Reexamination Certificate
active
06188904
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to a co-pending application entitled “METHOD FOR IMPROVING COMMUNICATION COVERAGE IN MULTI-CELL COMMUNICATION SYSTEMS USING LOCATION INFORMATION”, filed on even date herewith, and assigned to the assignee of the instant application.
1. Field of the Invention
The present invention relates generally to wireless communication systems and, in particular, to improving communication coverage in multi-cell wireless communication systems.
2. Background of the Invention
Multi-cell wireless communication systems are well known. Such systems have stationary fixed network equipment (FNE) and subscribers which are mobile. The FNE comprises a plurality of cell sites distributed across a geographic region but all linked to switching and control devices. A particular cell site is able to provide communication to the subscriber units within the cell's service coverage area. By interconnecting and distributing such cells in an adjacent fashion, a much broader, combined coverage area is created. Subscriber units anywhere in this combined area, then, are able to obtain communication through the cell site of at least one of the cells. Such a subscriber unit may be traveling across the system while involved in communication. The subscriber unit's communication will be provided by a serving cell, but as the unit approaches the edge of this cell's coverage area the communication must be handed-off to another cell if it is to be maintained.
Handing-off communication between cells is known in multi-cell communication systems. Subscriber units are provided with a neighbor cell list from the FNE whenever a communication is established and also when a communication is handed-off. The neighbor cell list serves as a list of possible hand-off targets for the subscriber unit. Problems arise, however, when a subscriber unit is prevented from handing-off to cells in its neighbor cell list. This may occur because the neighbor cell is congested and has no available resources. The serving cell will continue to provide the subscriber unit communication, but if the unit continues moving away from the serving cell radio reception problems will reduce the quality if not terminate the communication altogether. A multi-cell radio communication system can truly provide broad communication coverage only if the communication units are able to successfully hand-off to neighboring cells.
As multi-cell systems mature to support the explosive growth in the number of subscriber units, cells are becoming smaller. For example, additional cells are being added to cover particularly dense areas such as office buildings and stadiums. The result is much greater overlap in the coverage areas of individual cells. It is not uncommon for a cell's coverage area to extend well into the coverage area of a second cell.
This poses two problems for hand-offs facilitated by neighbor cell lists as they are used today. The additional overlapping of cells makes for longer and longer neighbor cell lists. Longer neighbor cell lists consume more bandwidth each time they are transmitted and consume more subscriber unit processing and memory resources to manage. Secondly, a subscriber unit is provided only with the neighbor cell list of the serving cell, but it may travel completely across a neighbor cell without handing-off the communication provided by the serving cell. The subscriber unit may well be within the coverage areas of cells which are not in its neighbor cell list, and to which it could possibly hand-off were these cells not absent from its neighbor cell list.
Therefore, a need exists for a method to provide subscriber units with improved hand-off techniques which overcome the deficiencies of the prior art.
REFERENCES:
patent: 4670899 (1987-06-01), Brody et al.
patent: 5794149 (1998-08-01), Hoo
patent: 5854981 (1998-12-01), Wallstedt et al.
patent: 5896570 (1999-04-01), Saunders et al.
patent: 5905950 (1999-05-01), Anell
patent: 5915221 (1999-06-01), Sawyer et al.
patent: 5946625 (1999-08-01), Hassan et al.
Bost Dwayne
Davis Temica M.
Jacobs Jeffrey K.
Motorola Inc.
LandOfFree
Method for improving communication coverage in multi-cell... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for improving communication coverage in multi-cell..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for improving communication coverage in multi-cell... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2568126